Device for improving carbon segregation of high-carbon tool steel and production process of tool steel

Abstract

The device for improving the carbon segregation of the high-carbon tool steel comprises a crystallizer, a submersed nozzle, a plurality of guide pipes, metal wires and a wire feeding mechanism, the guide pipes are vertically arranged above the crystallizer, and the guide pipes are located in the middle of the crystallizer in the width direction and arranged on the two sides of the submersed nozzle; the distance between the guide pipe adjacent to the immersion nozzle and the immersion nozzle is 200-350 mm, the distance between the guide pipe adjacent to the narrow edge of the crystallizer and the narrow edge of the crystallizer is 200-350 mm, and the metal wire is driven by the wire feeding mechanism to penetrate through the guide pipes to be vertically immersed in molten steel. According to the method, the metal wire is fed in the continuous casting process, the temperature deviation in the thickness direction of the continuous casting blank is reduced, meanwhile, the nucleating agent is introduced into the thickness center of the continuous casting blank, and therefore in the blank shell forming process of the casting blank, isometric crystals can be formed in the center, formation of developed columnar crystals is restrained, and composition segregation in the casting blank is reduced. The layering phenomenon of the product is avoided, the product quality is improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking and continuous casting, and in particular relates to a device for improving carbon segregation of high-carbon tool steel and a production process of tool steel. Background Art

[0002] High-carbon tool steel has a carbon content exceeding 0.80% and a hardness exceeding 60HRC after quenching and in use. This steel exhibits high hardness and excellent wear resistance. The traditional production process for high-carbon steel products is: steelmaking - refining - continuous casting - heating in a heating furnace - rolling - and heat treatment. Steelmaking is typically performed in a converter, followed by refining in LF and RH refining units. Continuous casting is performed using a continuous casting machine. The ingot is fed into the heating furnace, heated to a specific temperature and soaked for a specified period according to a prescribed heating schedule, before being rolled into steel plates of a specified shape and size. Appropriate heat treatment is then applied to adjust the properties of the steel plates. However, the high carbon content can easily lead to compositional segregation during the continuous casting process, resulting in uneven performance and microstructure. This can also lead to defects such as cracking during processing, seriously impacting product quality.

[0003] Chinese patent application number 200910012026.7 discloses a "method for reducing carbon segregation within high-carbon steel." The invention utilizes a production process consisting of steelmaking, refining, continuous casting, heating in a heating furnace, and continuous rolling. The invention is characterized in that the heating time in the heating furnace is ≤1.5 hours, the soaking time is ≥2.0 hours, and the total heating time is ≤3.5 hours. The furnace temperature is 1150-1250°C, the start rolling temperature is 1100-1250°C, and the final rolling temperature is ≥900°C. Compositional segregation within the continuously cast slab is macrosegregation, and altering this through high-temperature diffusion in the heating furnace is limited in effectiveness. It is difficult to achieve sufficient and uniform diffusion of carbon. Furthermore, prolonged high-temperature heating of the slab can lead to severe surface decarburization, which affects the performance of the steel plate. Furthermore, due to the excessive thickness of the slab, the carbon concentration in the central region is high, making it difficult to diffuse sufficiently outward. Consequently, cracking caused by compositional segregation still occurs during subsequent processing.

[0004] In summary, the carbon content of high-carbon tool steel produced by existing technology is prone to component segregation during the continuous casting process, resulting in uneven performance and structure, and defects such as cracking are prone to occur during the processing process, seriously affecting the quality of the product. Summary of the Invention

[0005] The purpose of the present invention is to provide a device for improving carbon segregation of high carbon tool steel and a production process for tool steel, which can significantly improve the segregation phenomenon of the product, significantly improve the quality of the steel, and avoid the problem of cracking of the product.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A device for improving carbon segregation in high-carbon tool steel comprises a crystallizer, an immersion nozzle, a conduit, a metal wire, and a wire feeding mechanism. Several of the conduits are vertically arranged above the crystallizer. The conduits are located in the middle of the width direction of the crystallizer and on both sides of the immersion nozzle. The conduits adjacent to the immersion nozzle are 200 to 350 mm away from the immersion nozzle, and the conduits adjacent to the narrow side of the crystallizer are 200 to 350 mm away from the narrow side of the crystallizer. Driven by the wire feeding mechanism, the metal wire passes through the conduits and vertically immerses into the molten steel.

[0008] The metal wire is a metal cored wire, the outer skin of the metal cored wire is a carbon steel skin, and the core powder of the metal cored wire is composed of steel powder consistent with the composition of the molten steel and one or two of titanium carbide and lanthanum cerium rare earth oxide, wherein the steel powder accounts for 70% to 80% of the total core powder, and the rest accounts for 20% to 30%.

[0009] The thickness of the carbon steel sheet is 0.5-1.5 mm, the particle size of the steel powder is 150-350 μm, and the particle sizes of titanium carbide and lanthanum-cerium rare earth oxide are both 0.2-0.5 μm.

[0010] The diameter of the metal wire is φ18-24 mm.

[0011] There are 2 to 6 catheters.

[0012] The wire feeding mechanism includes a metal wire drum and a pinch roller. The metal wire is wound on the metal wire drum and passed between the upper and lower pinch rollers. The wire is fed into the conduit under the drive of the friction force of the pinch rollers.

[0013] A production process for improving carbon segregation in high-carbon tool steel includes molten iron pretreatment, smelting, continuous casting, continuous casting billet heating, continuous casting billet rolling and heat treatment. The continuous casting process uses a device for improving carbon segregation in high-carbon tool steel, specifically including the following contents:

[0014] 1) Hot metal pretreatment: Desulfurize the hot metal by mixing lime and magnesium powder. The sulfur content of the hot metal is controlled to be ≤0.0010%. After pretreatment and desulfurization, more than 85% of the slag is removed.

[0015] 2) Converter smelting: top and bottom double-blown converter is used for smelting. The active oxygen content of the converter is ≤0.040%, the phosphorus content is ≤0.010%, the sulfur content is ≤0.0040%, and the slag amount at the converter tapping is less than 3kg / t steel.

[0016] 3) Refining: LF+RH process is adopted. During the LF refining process, the molten steel is modified, slag-making, deep desulfurization, micro-alloying and removal of sulfide and oxide inclusions in the molten steel. During the RH refining process, the molten steel is degassed and inclusions are further reduced to achieve N ≤ 0.0030% and TO ≤ 0.0020% in the molten steel.

[0017] 4) Continuous casting: During the continuous casting process, the superheat of the molten steel is 15-23°C. With the start of continuous casting, a metal wire is fed into the crystallizer. According to the slab width of 1200-2000 mm, the speed of feeding the metal wire is 0.9-1.1 times the continuous casting slab drawing speed. The wire feeding position in the crystallizer is 200-350 mm away from the immersion nozzle and the narrow side of the crystallizer, respectively. The direction of the wire feeding is parallel to the continuous casting slab drawing direction under the action of the guide tube; the metal wire enters the crystallizer vertically, and under the action of the high-temperature molten steel, the outer carbon steel skin is rapidly melted, and the internal steel powder is scattered near the center of the molten steel thickness below the protective slag. The steel powder absorbs heat and melts in the high-temperature molten steel, while the temperature near the center of the molten steel thickness is reduced. At the same time, the core powder contains one or two of titanium carbide and lanthanum cerium rare earth oxides as nucleating agents to promote the formation of equiaxed crystals in the center of the continuous casting slab.

[0018] The molten steel is poured into the tundish and sampled. The chemical composition of the molten steel in each heat is controlled as follows by weight percentage: C: 0.82%~0.88%, Si: 0.15%~0.25%, Mn: 0.38%~0.48%, P≤0.01%, S≤0.003%, Cr: 0.15%~0.25%, Ni≤0.15%, Cu≤0.15%, and the rest is Fe and unavoidable impurities.

[0019] 5) Continuous Casting Billet Heating: The billet temperature entering the heating furnace should be ≥650°C, the heating time should be ≤1.2h, the soaking time should be ≥1.0h, and the total soaking time should be ≤2.2h. The discharge temperature should be between 1050°C and 1100°C. Increasing the billet temperature in the heating furnace is beneficial for full austenitization of the billet structure, but excessively high temperatures increase energy consumption. Prolonging the soaking time is beneficial for the diffusion and homogenization of various elements in the steel, but excessively long soaking time may deteriorate the internal structure of the billet.

[0020] 6) Rolling and heat treatment: The ingot heated in the soaking furnace is sent to hot rolling, with the starting rolling temperature of 1000-1050℃, the final rolling temperature ≥860℃, and the steel plate thickness of 5-25mm. The finished hot-rolled steel plate is then heated to 1010-1080℃ for 10-50min, water quenched at 760-850℃, and then low-temperature tempering treatment is performed with the heating temperature of 170-190℃ and the holding time of 20-100min.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The device and process for improving carbon segregation in high-carbon tool steel of the present invention reduces the temperature deviation in the thickness direction of the continuous casting billet by feeding a metal wire during the continuous casting process. At the same time, a nucleating agent is introduced into the thickness center of the continuous casting billet, so that equiaxed crystals are formed in the center of the billet during the process of forming the billet shell, thereby inhibiting the formation of developed columnar crystals and reducing the component segregation inside the billet.

[0023] 2. The device and process for improving carbon segregation of high-carbon tool steel of the present invention effectively reduces the differences in structure and performance inside the steel plate caused by component segregation in the subsequent processing of the steel plate, avoids the occurrence of product stratification, improves product quality, and reduces production costs.

[0024] 3. The device and process for improving carbon segregation of high-carbon tool steel of the present invention greatly reduces the degree of carbon segregation in the continuous casting billet, reduces the heating time of the continuous casting billet in the heating furnace for high-temperature diffusion, improves the efficiency of the heating furnace and subsequent steel rolling, and reduces production costs.

[0025] 4. The device for improving carbon segregation of high-carbon tool steel used in the present invention has a simple structure, low investment, and does not affect the normal operation of other equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the device for improving carbon segregation in high carbon tool steel according to the present invention.

[0027] In the figure: 1. Immersion nozzle; 2. Conduit; 3. Metal wire; 4. Crystallizer; 5. Protective slag; 6. Core powder; 7. Molten steel; 8. Continuous casting shell; 9. Equiaxed crystal; 10. Motor; 11. Metal wire reel; 12. Pinch roller. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the specific implementation methods of the present invention are further described below in conjunction with examples. The following examples are used to specifically illustrate the contents of the present invention. These examples are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0029] A device for improving carbon segregation in high-carbon tool steel comprises a crystallizer 4, an immersion nozzle 1, a conduit 2, a metal wire 3, and a wire feeding mechanism. Several conduits 2 are vertically arranged above the crystallizer 4. The conduits 2 are located in the middle of the width of the crystallizer 4 and on both sides of the immersion nozzle 1. The conduits 2 adjacent to the immersion nozzle 1 are 200 to 350 mm away from the immersion nozzle, and the conduits 2 adjacent to the narrow side of the crystallizer 4 are 200 to 350 mm away from the narrow side of the crystallizer 4. Driven by the wire feeding mechanism, the metal wire 3 passes through the conduits 2 and vertically immerses into the molten steel 7.

[0030] The metal wire 3 is a metal cored wire, the outer skin of which is a carbon steel skin. The core powder of the metal cored wire is composed of steel powder having the same composition as the molten steel and one or two of titanium carbide and lanthanum cerium rare earth oxides, wherein the steel powder accounts for 70% to 80% of the total core powder, and the rest accounts for 20% to 30%.

[0031] The thickness of the carbon steel sheet is 0.5-1.5 mm, the particle size of the steel powder is 150-350 μm, and the particle sizes of titanium carbide and lanthanum-cerium rare earth oxide are both 0.2-0.5 μm.

[0032] The diameter of the metal wire 3 is φ18-24 mm.

[0033] There are 2 to 6 catheters 2.

[0034] The wire feeding mechanism includes a wire drum 11 and a pinch roller 12. The wire 3 is wound around the wire drum 11 and passed between the upper and lower pinch rollers 12. The wire 3 is fed into the conduit 2 under the friction of the pinch rollers 12. Both the wire drum 11 and the pinch rollers 12 are driven to rotate by a motor.

[0035] A production process for improving carbon segregation in high-carbon tool steel includes molten iron pretreatment, smelting, continuous casting, continuous casting billet heating, continuous casting billet rolling and heat treatment. The continuous casting process uses a device for improving carbon segregation in high-carbon tool steel, specifically including the following contents:

[0036] 1) Hot metal pretreatment: Desulfurize the hot metal by mixing lime and magnesium powder. The sulfur content of the hot metal is controlled to be ≤0.0010%. After pretreatment and desulfurization, more than 85% of the slag is removed.

[0037] 2) Converter smelting: top and bottom double-blown converter is used for smelting. The active oxygen content of the converter is ≤0.040%, the phosphorus content is ≤0.010%, the sulfur content is ≤0.0040%, and the slag amount at the converter tapping is less than 3kg / t steel.

[0038] 3) Refining: LF+RH process is adopted. During the LF refining process, the molten steel is modified, slag-making, deep desulfurization, micro-alloying and removal of sulfide and oxide inclusions in the molten steel. During the RH refining process, the molten steel is degassed and inclusions are further reduced to achieve N ≤ 0.0030% and TO ≤ 0.0020% in the molten steel.

[0039] 4) Continuous casting: During the continuous casting process, the superheat of the molten steel is 15-23°C. With the start of continuous casting, a metal wire is fed into the crystallizer. According to the slab width of 1200-2000 mm, the speed of feeding the metal wire is 0.9-1.1 times the continuous casting slab drawing speed. The wire feeding position in the crystallizer is 200-350 mm away from the immersion nozzle and the narrow side of the crystallizer, respectively. The direction of the wire feeding is parallel to the continuous casting slab drawing direction under the action of the guide tube; the metal wire enters the crystallizer vertically, and under the action of the high-temperature molten steel, the outer carbon steel skin is rapidly melted, and the internal steel powder is scattered near the center of the molten steel thickness below the protective slag. The steel powder absorbs heat and melts in the high-temperature molten steel, while the temperature near the center of the molten steel thickness is reduced. At the same time, the core powder contains one or two of titanium carbide and lanthanum cerium rare earth oxides as nucleating agents to promote the formation of equiaxed crystals in the center of the continuous casting slab.

[0040] The molten steel is poured into the tundish and sampled. The chemical composition of the molten steel in each heat is controlled as follows by weight percentage: C: 0.82%~0.88%, Si: 0.15%~0.25%, Mn: 0.38%~0.48%, P≤0.01%, S≤0.003%, Cr: 0.15%~0.25%, Ni≤0.15%, Cu≤0.15%, and the rest is Fe and unavoidable impurities.

[0041] 5) Continuous Casting Billet Heating: The billet temperature entering the heating furnace should be ≥650°C, the heating time should be ≤1.2h, the soaking time should be ≥1.0h, and the total soaking time should be ≤2.2h. The discharge temperature should be between 1050°C and 1100°C. Increasing the billet temperature in the heating furnace is beneficial for full austenitization of the billet structure, but excessively high temperatures increase energy consumption. Prolonging the soaking time is beneficial for the diffusion and homogenization of various elements in the steel, but excessively long soaking time may deteriorate the internal structure of the billet.

[0042] 6) Rolling and heat treatment: The ingot heated in the soaking furnace is sent to hot rolling, with the starting rolling temperature of 1000-1050℃, the final rolling temperature ≥860℃, and the steel plate thickness of 5-25mm. The finished hot-rolled steel plate is then heated to 1010-1080℃ for 10-50min, water quenched at 760-850℃, and then low-temperature tempering treatment is performed with the heating temperature of 170-190℃ and the holding time of 20-100min.

[0043] The metal wire 3 has a cylindrical cross-section, with an iron sheet on the outside and core powder 6 wrapped on the inside. The metal wire 3 is wound on a metal wire reel 11 before use. After continuous casting starts, molten steel 7 is poured into the crystallizer 4 from the immersion water inlet 1. As the continuous casting starts, the metal wire 3 is delivered forward along with the pinch roller 12 under the drive of the motor 10. At the same time, under the guidance of the conduit 2, it enters the crystallizer 4 vertically. Under the action of the high-temperature molten steel 7, the outer iron sheet of the metal wire 3 is rapidly melted, and the inner core powder 6 is scattered near the center of the molten steel thickness below the protective slag 5. The core powder 6 absorbs heat and melts in the high-temperature molten steel 7, and at the same time, the temperature near the center of the thickness of the molten steel 7 is reduced. The crystallizer 4 is composed of water-cooled copper plates. Due to copper's excellent thermal conductivity, the temperature of the molten steel 7 drops rapidly around the mold. After the steel powder is fed into the center of the thickness, the temperature of the molten steel 7 drops to approximately the same level as the rest of the mold. Simultaneously, nucleating agents such as titanium carbide and lanthanum-cerium rare earth oxides act as nuclei at the center of the thickness, generating a large number of equiaxed crystals 9 within the cross-section of the ingot. This increased proportion of equiaxed crystals 9 eliminates the segregation at the center of the thickness caused by developed columnar crystals. Upper and lower pinch rollers 12 compress the wire 3. As the pinch rollers 12 rotate, friction forces the wire 3 into the mold. The guide tube 2 is welded to the underside of the tundish car.

[0044] The thickness of the continuous casting slabs produced in the examples and comparative examples is 250 mm. The relevant parameters during molten iron pretreatment, converter smelting, and refining are shown in Table 1. The relevant parameters of the examples and comparative examples during continuous casting are shown in Table 2. The chemical composition of the tundish in the examples and comparative examples is shown in Table 3. The relevant parameters of the examples and comparative examples during continuous casting, rolling, and heat treatment are shown in Table 4. The relevant parameters of the product performance of the examples and comparative examples are shown in Table 5.

[0045] Table 1 Parameters of various parts of the nozzle

[0046] Example Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Sulfur content of molten iron, % 0.0008 0.0009 0.0010 0.0009 0.0008 0.0008 0.0009 Proportion of slag removed, % 89 85 90 92 88 87 91 Active oxygen at converter end point, % 0.036 0.039 0.040 0.037 0.038 0.038 0.039 Phosphorus content at converter end point, % 0.009 0.0010 0.008 0.009 0.008 0.008 0.009 Sulfur content at converter end point, % 0.0040 0.0035 0.0038 0.0036 0.0039 0.0037 0.0036 Slag quantity during tapping, kg / t 2.8 2.9 3.0 2.7 2.9 2.8 2.9 Refining N, % 0.0026 0.0028 0.0027 0.0030 0.0029 0.0028 0.0027 Refined TO, % 0.0016 0.0018 0.0019 0.0015 0.0020 0.0017 0.0016

[0047] Table 2 Continuous casting related parameters

[0048]

[0049]

[0050] Table 3 Chemical composition of the package wt / %

[0051] Example Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 C 0.82 0.83 0.85 0.87 0.88 0.84 0.85 Si 0.15 0.16 0.20 0.22 0.25 0.21 0.19 Mn 0.38 0.41 0.43 0.45 0.48 0.41 0.43 P 0.010 0.009 0.008 0.010 0.01 0.009 0.01 S 0.0010 0.0009 0.0010 0.0008 0.0009 0.0009 0.0010 Cr 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Ni 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Cu 0.15 0.15 0.15 0.15 0.15 0.15 0.15

[0052] Table 4 Parameters related to billet heating, rolling and heat treatment

[0053] Example Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Temperature of billet entering heating furnace, ℃ 650 653 670 665 658 659 663 Heating time, h 1.2 1.0 1.1 1.2 1.0 1.5 1.6 Soaking time, h 1.0 1.1 1.0 1.0 1.1 1.5 1.5 The total time is h 2.2 2.1 2.1 2.2 2.1 3.0 3.1 Oven temperature, ℃ 1050 1100 1060 1070 1080 1090 1100 Rolling temperature, ℃ 1000 1022 1037 1043 1050 1036 1042 Finish rolling temperature, ℃ 860 865 874 869 872 868 874 Steel plate thickness, mm 5 10 15 20 25 10 15 Steel plate heating temperature, ℃ 1010 1022 1043 1061 1080 1055 1048 Holding time, min 10 20 30 40 50 20 30 Water quenching temperature, ℃ 760 782 804 807 850 800 796 Tempering temperature, ℃ 17O 175 18O 185 190 178 186 Holding time, min 20 40 60 80 100 40 60

[0054] Table 5 Performance related parameters of the examples and comparative examples

[0055]

[0056] In summary, as can be seen in Table 5, the average carbon segregation index for the example steel was 0.034, the average hardness difference between the center and edge of the thickness was 1 HRC, and the steel plate showed no delamination. The average carbon segregation index for the comparative steel steel was 0.26, the average hardness difference between the center and edge of the thickness was 8 HRC, and the steel plate occasionally exhibited delamination. Using this method to produce high-carbon tool steel, segregation in the thickness direction of the steel plate was significantly reduced, the hardness difference of the steel plate was reduced, and the steel plate had good processability. Delamination due to internal component segregation was avoided, thereby improving product quality stability and reducing production costs.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for improving carbon segregation in high carbon tool steel, characterized in that: The invention comprises a crystallizer, an immersion water inlet, a conduit, a metal wire, and a wire feeding mechanism. Several of the conduits are vertically arranged above the crystallizer. The conduits are located in the middle of the width direction of the crystallizer and on both sides of the immersion water inlet. The conduits adjacent to the immersion water inlet are 200 to 350 mm away from the immersion water inlet, and the conduits adjacent to the narrow side of the crystallizer are 200 to 350 mm away from the narrow side of the crystallizer. Driven by the wire feeding mechanism, the metal wire passes through the conduit and vertically immerses into the molten steel.

2. The device for improving carbon segregation of high carbon tool steel according to claim 1, characterized in that: The metal wire is a metal cored wire, the outer skin of the metal cored wire is a carbon steel skin, and the core powder of the metal cored wire is composed of steel powder consistent with the composition of the molten steel and one or two of titanium carbide and lanthanum cerium rare earth oxide, wherein the steel powder accounts for 70% to 80% of the total core powder, and the rest accounts for 20% to 30%.

3. The device for improving carbon segregation of high carbon tool steel according to claim 2, characterized in that: The thickness of the carbon steel sheet is 0.5-1.5 mm, the particle size of the steel powder is 150-350 μm, and the particle sizes of titanium carbide and lanthanum-cerium rare earth oxide are both 0.2-0.5 μm.

4. A device for improving carbon segregation in high carbon tool steel according to any one of claims 1 to 3, characterized in that: The diameter of the metal wire is φ18-24 mm.

5. The device for improving carbon segregation of high carbon tool steel according to claim 1, characterized in that: There are 2 to 6 catheters.

6. The device for improving carbon segregation of high carbon tool steel according to claim 1, characterized in that: The wire feeding mechanism includes a metal wire drum and a pinch roller. The metal wire is wound on the metal wire drum and passed between the upper and lower pinch rollers. The wire is fed into the conduit under the drive of the friction force of the pinch rollers.

7. A production process for improving carbon segregation in high-carbon tool steel, comprising molten iron pretreatment, smelting, continuous casting, continuous casting billet heating, continuous casting billet rolling and heat treatment, characterized in that: The device for improving carbon segregation of high carbon tool steel according to any one of claims 1 to 6 is used in the continuous casting process, specifically comprising the following contents: Continuous casting: During the continuous casting process, the superheat of the molten steel is 15-23°C. As the continuous casting process begins, a metal wire is fed into the crystallizer at a speed of 0.9-1.1 times the continuous casting speed. The wire feeding position in the crystallizer is 200-350 mm away from the immersion nozzle and the narrow side of the crystallizer, respectively. The wire feeding direction is parallel to the continuous casting direction under the action of the guide tube. The metal wire enters the crystallizer vertically. Under the action of the high-temperature molten steel, the outer carbon steel skin melts rapidly, and the internal steel powder is scattered near the center of the molten steel thickness below the protective slag. The steel powder absorbs heat and melts in the high-temperature molten steel, while the temperature near the center of the molten steel thickness drops. Continuous casting billet heating: The temperature of the continuous casting billet when entering the heating furnace is ≥650℃, the heating time is ≤1.2h, the soaking time is ≥1.0h, the total time is ≤2.2h, and the furnace discharge temperature is 1050℃~1100℃.

8. The production process for improving carbon segregation in high carbon tool steel according to claim 7, characterized in that: Hot metal pretreatment uses a mixture of lime and magnesium powder for desulfurization. The sulfur content of the hot metal is controlled at ≤0.0010%. After pretreatment and desulfurization, more than 85% of the slag is removed. Smelting is carried out in a top-bottom combined-blown converter. The converter endpoint active oxygen content is ≤0.040%, phosphorus content is ≤0.010%, and sulfur content is ≤0.0040%. The converter tapping slag volume is less than 3kg / t steel. The refining adopts LF+RH process, and N≤0.0030% and TO≤0.0020% in the molten steel.

9. The production process for improving carbon segregation in high carbon tool steel according to claim 7, characterized in that: Rolling and heat treatment of continuous casting billet: the starting rolling temperature is 1000-1050℃, the final rolling temperature is ≥860℃, the steel plate thickness is 5-25mm, and then the finished hot-rolled steel plate is heated to 1010-1080℃, the holding time is 10-50min, water quenched at 760-850℃, and then low-temperature tempering treatment is performed, the heating temperature is 17O-190℃, and the holding time is 20-100min.

10. The production process for improving carbon segregation in high carbon tool steel according to claim 7, characterized in that: The chemical composition of the molten steel is controlled to be: C: 0.82% to 0.88%, Si: 0.15% to 0.25%, Mn: 0.38% to 0.48%, P≤0.01%, S≤0.003%, Cr: 0.15% to 0.25%, Ni≤0.15%, Cu≤0.15%, and the rest is Fe and unavoidable impurities.

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